可以使用 put one's foot down 這個片語喔 ，表面上就是把腳放下的意思~

[例句] I don't agree ! I've got to put down my foot down! 我不同意! 我要採取堅定的立場!

I don't agree ! I've got to put down my foot down!還是I don't agree ! I've got to put my foot down! …是不是多打了一個down

Pin_Hao_Chiu: 不好意思~多打了一個down !! 是I don't agree ! I've got to put my foot down!

I have to firm on it~(口語化,文法有誤) from I am Sam(movie)